The coefficient of x4 is the expansion of (1 + x + x2)10 is _____.
Answer (integer)
615
Solution
(1 + x + x<sup>2</sup>)<sup>10</sup>
<br><br>= <sup>10</sup>C<sub>0</sub>(1 + x)<sup>10</sup> + <sup>10</sup>C<sub>1</sub>(1 + x)<sup>9</sup>.x<sup>2</sup> + <sup>10</sup>C<sub>2</sub>(1 + x)<sup>8</sup>.x<sup>4</sup>+ .....
<br><br>Coefficient of x<sup>4</sup>
<br><br>= <sup>10</sup>C<sub>0</sub>.<sup>10</sup>C<sub>4</sub> + <sup>10</sup>C<sub>1</sub>.<sup>9</sup>C<sub>2</sub> + <sup>10</sup>C<sub>2</sub>.<sup>8</sup>C<sub>0</sub>
<br><br>= 210 + 360 + 45
<br><br>= 615
About this question
Subject: Mathematics · Chapter: Binomial Theorem · Topic: Binomial Expansion
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